1. Field of the Invention
The present invention relates to an armrest assembly, more particularly to a height adjustable armrest assembly for a chair.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional height adjustable armrest assembly 1 is shown to include an L-shaped support 11, a vertical sleeve 12, a lever body 13, and an armrest 14.
The support 11 includes a horizontal part 111 adapted to be fixed on a bottom side of a chair (not shown), and a vertical part 112 that extends upwardly from one end of the horizontal part 111 and that is formed with vertically aligned positioning grooves 113. The vertical sleeve 12 is sleeved slidably on the vertical part 112, has a peripheral wall 121 defining a receiving space 122 for receiving the vertical part 112 therein, and is formed with a plurality of limiting ribs 123 which contact slidably the vertical part 112 so as to prevent wobbling of the peripheral wall 121 relative to the vertical part 112. The lever body 13 has an upper block portion 132 pivoted to the peripheral wall 121, an engaging portion 133 extending from the upper block portion, 132 into the receiving space 122 to releasably engage a selected one of the positioning grooves 113, and an operating portion 131 connected to the upper block portion 132 and exposed from the peripheral wall 121. The armrest 14 is mounted on the vertical sleeve 12. When the operating portion 131 is lifted upward as shown in FIG. 2, the lever body 13 swings in the vertical sleeve 12 to permit disengagement of the engaging portion 133 from the selected one of the positioning grooves 113.
It is relatively inconvenient and laborious to adjust the height of the armrest 14. Moreover, since the distance between adjacent ones of the positioning grooves 113 is fixed, height adjustment of the conventional armrest assembly lacks flexibility.
A height adjustable armrest assembly for a chair according to U.S. Pat. No. 5,908,221 discloses an armrest support adapted to be fixed on a seat of the chair, an armrest mounted rotatably on the armrest support, a hydraulic cylinder secured in the armrest support, a piston rod secured to the armrest and exposed to ambience when the armrest is lifted relative to the armrest support by the piston rod, and a lever unit mounted in the armrest for actuating the piston rod.
Disadvantages of Patent ""221 are as follows:
(1) Since the outer surface of the piston rod is normally applied with lubricant thereon, the user may accidentally contact the lubricant when the piston rod is raised and exposed to the ambience.
(2) Since the armrest and the top end of the armrest support cooperatively form a gap therebetween when the piston rod is raised, objects, such as clothes, fingers, etc., may be accidentally clamped therebetween when the armrest together with the piston rod is lowered down to the top end of the armrest support.
Therefore, the object of this invention is to provide a height adjustable armrest assembly for a chair that is capable of overcoming the aforesaid disadvantages of the prior art.
Accordingly, a height adjustable armrest assembly of the present invention for a chair includes: a support unit including a lower part defining a lower chamber, and an upper part that defines an upper chamber therein, that is movable relative to the lower part, and that has an abutting member disposed within the upper chamber and subdividing the upper chamber into an upper portion and a lower portion; an armrest mounted on the upper part so as to be movable together therewith; a cylinder-and-piston unit including a cylinder that extends into the lower portion of the upper chamber to abut against the abutting member and that has opposite upper and lower ends, a piston mounted securely in the lower chamber and telescopically extending into the lower end of the cylinder, and a locking member including a spring-biased button projecting upwardly from the upper end of the cylinder, extending through the abutting member and into the upper portion of the upper chamber, and pressible to move between a locked position, in which, the cylinder is locked by the locking member against axial movement relative to the piston, and an unlocked position, in which, the cylinder is released by the locking member so as to be axially movable relative to the piston; and a control knob mounted movably on the upper part of the support unit, engaging the button, and operable so as to move the button from the locked position to the unlocked position.